1. Field of the Invention
This invention relates to lighting fittings of the kind designed for use with electric lamps providing a relatively compact high intensity light source, as may be employed, for example, in studios, theatres, outside locations and other situations where a high degree of directional lighting is required.
2. Description of Related Art
The spread of the light beam produced by such a fitting is often required to be varied so as to enable the fitting to operate in either the spot-light or flood mode, and for this purpose the lamp is commonly supported on a movable carriage with a concave reflector mounted behind it, the carriage assembly being movable towards or away from a Fresnel lens.
A major disadvantage of such an arrangement is that the flux pick up from the lamp is small, particularly for the spot position, when the lamp is furthest from the lens.
A further disadvantage is that an appreciable proportion of the radiations incident upon the reflector are reflected back towards the lamp, resulting in a loss of light, due to absorption, and an increased heating of the lamp, with a consequent shortening of the lamp life due to seal failure.
Although it is possible to utilise a wrap-around reflector, i.e. one that extends forwardly beyond the lamp, to pick up and control a greater proportion of the lamp flux than is possible with a simple concave reflector mounted behind the lamp, a satisfactory change in beam spread between desired spot and flood modes cannot be achieved in such a case simply by moving the lamp along the reflector axis.